(1) Field of the Invention
THIS INVENTION relates to a pneumatic percussion hammer.
(2) Prior Art
Pneumatic percussion hammers are well-known and widely used in rock drilling, such a hammer being described and illustrated in the specification of my Australian Patent No. 493847. Although hammers according to this Patent have been found to be very efficient in operation, they are not able to provide uncontaminated core samples as the rock fragments carried by the flow of air up the bore hold, outside the hammer and the drill tube onto which the hammer is screwed, will be likely to detach fragments from the sides of the bore hole and the air flow will carry these as well as fragments from the bottom of the hole.